Intense white spherical flash above a full rainbow. UNREALI was standing on my deck at around 6:15 pm with a neighbor talking as we admired a perfect rainbow that had formed to our east. As we were talking looking at the rainbow suddenly from nowhere appeared a bright white spherical flash that was of great intensity. This flash was a sphere with flared edges and maybe the diameter of a 1/3 full moon. The flash of white light appeared to have lasted for maybe 300 milliseconds. Just long enough to get a clear view. It was so intense that had the duration lasted longer you couldn't stare at it. Very similar to the intensity of the sun, except being smaller and of a pure white color. I have never seen anything supernatural in my life and I am a bit shaken at the moment. I stared at the spot in the sky until almost sunset hoping it would reappear, but it never did. 3 mins after this occurred I went inside to grab my iPad and I snapped 2 images of the rainbow. Now that I have reviewed the two images, I can see a black object near where the flash occurred. I will never forget this until the day I die and I now know 100% that there is an unexplained phenomena happening around us and I need answers. It was simply incredible.